Pi backlash: Fans call replacement 'misleading'

In the pi wars, the backlash has begun. Supporters of a campaign to replace pi with a new mathematical constant tau, equal to 2pi, say this would make calculations simpler. Now a
website called The Pi Manifesto suggests that tau itself is misleading.

For those who've missed this ongoing mathematical scuffle, physicist Michael Hartl last year published The Tau Manifesto, explaining that pi is an unnatural choice for the circle constant and we should all use tau instead. "Eventually I think there is going to be a groundswell of support for it," Hartl told New Scientist in an interview earlier this year.

That groundswell occurred last week on tau day, with supporters of the new constant making their voices heard in news outlets around the world. The Pi Manifesto attempts to redress the balance by pointing out holes in Hartl's arguments.

Central to Hartl's campaign is the fact that 2pi crops up in lots of well-known mathematical formulas, but as Michael Cavers, the mathematician at the University of Calgary who wrote The Pi Manifesto, points out, there are also many formulas that favour pi.

In a lot of instances, pi is more natural to use, but in other instances it makes more sense to use tau. It is not clear to me that one is strictly better than the other but it is certainly an interesting topic to discuss

Why write the Pi Manifesto? Cavers says there are many websites that support tau, but no one is actively defending pi. "The Pi Manifesto is a first draft meant to collect arguments and mathematical facts on why it is the correct circle constant."

He's not completely against tau though, and says the discussion could prompt people to find out more about maths. "The Tau Movement has definitely sparked an interest, and to me, intellectual curiosity is more important than which circle constant is the better one."

10 Comments

Looks rather silly to fight against or for mathematical constants which can both be used for various calculations. If one is better for some calculations, as they show there, the other one can also be used. So what's the fuss about?

AGreenhill
on July 7, 2011 5:39 PM

After reading the tau manifesto I took the document's advice and I did a review for myself, pouring back through my engineering and physics books. In the end I was rather dumb-founded at how often 2*pi shows up (nearly every time) and in cases where pi was alone or with another factor (such as 4*pi) it was actually enlightening to replace pi with tau. The numbers pi and 3 have always been my favorite numbers ~ despite that fact, I must agree, tau is the winner.

I am actively working in mathematics and logics, and I have a very negative look at any campaign around inessential trivialities - to me it has a strong self-promotional flavour. If you are working mathematician, you try to prove theorems, develop new theories etc. You may want to improve notation as a system, but to battle around a symbol? It is like to insist that the symbols for lines should begin with l and for points with p.

Shackman
on July 7, 2011 6:41 PM

Michael Hartl argues quotes in his Tau Manifesto something called "Pi day", happening at March 14th, relating to US notation of dates "3/14". Before arguing in favour of an internationally and historically accepted convention for very little benefit, I'd suggest that Americans reassess the distorted logic of placing days between months and years in dates, as this is the most convoluted system ever adopted. Then, maybe worry about decimalising those medieval length units based on some forgotten king's limbs, which in itself would enormously facilitate calculations all around; even the Brits have (mostly) moved away from imperial units... Then maybe we can discuss meddling with constants.

John
on July 7, 2011 7:14 PM

Exp(i*2*pi) = 1 just isn't as good as exp(i*pi) + 1= 0.

HB
on July 7, 2011 11:44 PM

What? How is a constant that differes from another constant by a factor of two even another constant at all? It's the same thing, surely it makes no difference.....

As for "this would make calculations simpler" -- generally we learn the skill needed to multiply a number by two well before we need to use pi.

I can only think of one situation where a single 'symbol' for 2pi would be nice, and that's a handheld calculator. It doesn't matter in computation. You can always define a constant or macro for 2pi, and the compiler will handle that constant just as fast as it handles pi.